Roman Empire Warms Up

Roman Empire warms up, according to reports in, ScienceDaily 9 July 2012, New Scientist 10 July 2012 and Nature Climate Change, DOI: 10.1038/nclimate1589. An international team of scientists led by Jan Esper of Johannes Gutenberg University Mainz has studied density of tree rings in old trees and preserved trees in Finnish Lapland. According to Esper, warm summer temperatures are associated with higher density in tree rings so they can be used to show trends in temperatures over the years the trees lived. Using their measurements the research team have reconstructed temperatures in northern Europe going back to 138 BC. A graph of their results shows cycles of warm and cool periods: a warm period during the Roman Empire followed by a cool period during the “migration era” following the collapse of the Roman Empire, then a warm period in the Middle Ages followed by the “Little Ice Age” and then the current warm period beginning around the time of the industrial revolution. These variations have been known about previously, but Esper stated, “We found that previous estimates of historical temperatures during the Roman era and the Middle Ages were too low”. This would explain why it was warm enough to grow grape vines in northern England during the Roman occupation of Britain. Although temperatures have varied, the overall trend has been a slight cooling over the two millennia. The scientists believe this is the result of small variations in the earth orbit known as Milankovitch wobbles, which result in less solar radiation on the earth.

Editorial Comment: The graph produced by this research indicates that both the Roman and Medieval warm periods were warmer than the current warm period. As neither of these periods were associated with industrialisation, they are therefore evidence that the association of the current warm period with the industrial revolution is a historical coincidence rather than cause and effect. It is interesting climate researchers are prepared to blame a natural phenomenon, i.e. variation in earth’s orbit, for the cooling, but not look for natural causes for the warm periods. Also, you may never have thought of it – but one reason the Christian Gospel was spread so quickly in the first few centuries was not just the Pax Romanus and the Roman military roadways, but the very important fact that the weather was very amenable to travel. (Ref. forests, weather)